1. Field of the Invention
The present invention relates to a still video camera for recording and reproducing image signals.
2. Description of the Prior Art
Recently, various recording and reproducing apparatuses for recording and/or reproducing video images, audio signals or other information signals have been developed and widely used. In these recording and reproducing apparatuses, a still video camera is an apparatus for recording a photographed picture in a magnetic disk together with various information related thereto and further reproducing the recorded photographed picture as a still visual image at need.
In the still video camera, the image signals of a subject to be photographed are photoelectrically transferred to luminance signals and color difference signals through solid-state imaging elements. These electric signals are FM-modulated and synthesized into multiplex image signals, and the obtained image signals, are recorded on tracks formed on a magnetic disk being rotated. In addition, ID data signals related to the photographed image signals such as the type of recording (field recording or frame recording), the track number, the date of the photography, etc. are DPSK-modulated (Differential Phase Shift Keying modulation) and recorded on the same magnetic disk so as to be overlapped on the image signals in accordance with a frequency multiplex system.
When the image signals recorded on the magnetic disk are reproduced, the FM-modulated luminance signals and the color difference signals are both stored in memory sections as digital data in accordance with sampling pulses generated on the basis of vertical and horizontal synchronizing signals extracted by the luminance signals. The data stored in the memory sections are read out in accordance with a predetermined clock signal. The read data is converted into analog signals corresponding thereto, and the analog signals are outputted to a video output terminal through an output circuit.
In the still video apparatuses represented by the still video camera as described above, when a frame recording is implemented by a still video apparatus provided with a magnetic head and a memory section for storing image signals, two field images are stored in the memory section, and the data corresponding to these two stored field images are recorded on a single track, respectively. In other words, two field images are recorded on two tracks. On the other hand, when erased, the image signals for one picture (i.e., the image signals for the two fields) are erased simultaneously. In this case, since the tracks on which the image signals are to be recorded are manually selected and then erased with a single head, there is a problem in that the tracks on which the data corresponding to another picture is recorded (which is not required to be erased) are erroneously erased.
However, in the conventional recording method by which luminance signals and linearly-sequenced color difference signals are recorded on the same track under overlap conditions, since the frequency band of the luminance signals cannot be overlapped with the frequency band of the color difference signals, the frequency bands of both the recorded luminance and the color difference signals are limited to a narrow range, respectively. Therefore, it was impossible to obtain high definition picture, that is, the picture produced from image signals with a wide frequency band cannot be so far recorded.
In order to overcome this problem, an improved still video apparatus has been proposed by one of the inventors in U.S. patent application Ser. No. 07/913,191. According to the still video apparatus, a high definition picture can be recorded by dividing image signals corresponding to one picture into a plurality of groups and further by recording the respective image signals into a plurality of tracks with an expanded time axis so that the frequency band of the image signals to be recorded can be substantially widened.
In the above-mentioned still video apparatus, when the luminance signals and two color difference signals which constitute image signals obtained in the frame recording or in the field recording are recorded on a plurality of different tracks, respectively, a recording pattern is determined, for example as follows. Namely, the luminance signals corresponding to the first field are recorded from the outermost circumferential track to the second track on a magnetic disk. The luminance signals corresponding to the second field are recorded from the succeeding track to the fourth track, and the color difference signals corresponding to the respective luminance signals are recorded from the succeeding track to the eighth track. Accordingly, in this example, eight tracks in total are required for recording image signals which constitute a single picture.
Therefore, in the case where image signals for one picture are recorded on the eight tracks as described above, when the image signals for one recorded picture become unnecessary, all the image signals recorded on the plurality of the tracks (on which the image signals for the unnecessary picture are recorded) must be erased.
In the meantime, in the proposed apparatus, one-track erasing method is usually adopted in order to erase the signals recorded on the tracks. In this method, the tracks on which the signals to be erased are recorded are selected manually, and then the recorded signals are erased track by track. However, according to this erasing method, since an erasing operation must be made in each track, a number of erasing operations are required in order to erase the image signals for one picture which are recorded in a plurality of tracks. Therefore, it takes a relatively long time to erase the image signals recorded on the tracks, which results in the troublesome in the erasing operations. Further, in this case, the tracks on which the image signals to be erased are not necessarily arranged in sequence on the magnetic disk, so that there is a possibility that only the image signals recorded on a part of a plurality of tracks (on which image signals for one picture are recorded) are erased imperfectly. Further, there is another possibility that a part of a plurality of tracks (on which image signals for the necessary picture are recorded) are erased erroneously against operator's will.
Further, the magnetic disk for the still video apparatus of this kind can be used in common with the conventional still video apparatus of such a type that image signals for one field are recorded on one track as already explained. In the conventional still video apparatus of this type, when the image signals recorded on the tracks are required to be erased, the one-track erasing method (the recorded image signals are erased in each track) is also performed. Therefore, when the magnetic disk (on which image signals are recorded under the condition that they are divided into a plurality of tracks) is used for the conventional still video apparatus, there is a possibility in that when the image signals for one picture are required to be erased, image signals recorded on a part of a plurality of tracks on which other necessary pictures are recorded (other than the tracks on which the image signals to be erased are recorded) are erroneously erased.
As described above, when the image signals recorded on the magnetic disk from which a part of a plurality of tracks (on which the image signals for one picture are recorded) has been erroneously erased are reproduced, it is impossible to reproduce a correct picture on the basis of the signals recorded on the remaining tracks.